A wide variety of compositions intended for improving the appearance of skin, including improving skin hydration and moisturization, are known in art. However, most of these moisturizing agents work either through formation of occlusive films on the skin that prevent transepidermal water loss (e.g., mineral oil, petrolatum and other oils), or through humectants that attract and retain moisture on the skin surface (e. g. glycerin, propylene glycol, butylene glycol and so on). There is a need for agents that protect the skin barrier more holistically.
Ampelopsis grossedentata or “Moyeam” is a species of plant belonging to the Vitaceae family, genus: Ampelopsis Michx. The specific name grossedentata comes from the plant's growing structure and leaves. It is mainly distributed in middle and south of China. It also finds presence in some south-east Asian countries. Moyeam is generally grown in Zhang Jiajie, the famous mountain in Hunan province of China. The leaves and stems are used to make a herbal tea popular by the name “Moyeam” in China. The tea is very popular among health-conscious consumers for its high levels of flavonoids especially Dihydromyricetin. Traditional uses include cure for respiratory diseases, eliminating inflammation, as an anti-oxidant, regulating blood sugar and fat and as an anti-cancer agent. Ampelopsis grossedentata is widely used as a medicinal plant. Its dried leaves and stems, also named as Vine Tea or Mao Yan Mei, have been consumed as a health tea and herbal medicine for hundreds of years. The chemical content of this plant includes flavonoids such as dihydromyricetin and myricetin (Du, Q.; Chen, P.; Jerz, G.; Winterhalter, P. Preparative separation of flavonoid glycosides in leaves extract of Ampelopsis grossedentata using high-speed counter-current chromatography. J. Chromatogr. A 2004, 1040, 147-149.). It was used as folk medicine or a daily drink for the treatment of hepatitis, flu, hypertension, hyperglycemic and sore throat. (Gao, J. H.; Liu, B. G.; Ning, Z. X.; Zhao, R. X.; Zhang, A. Y.; Wu, Q. Characterization and antioxidant activity of flavonoid-rich extracts from leaves of Ampelopsis grossedentata. J. Food Biochem. 2009, 33, 808-820.). Modern pharmacology studies have shown that it had activities such as anticancer, liver protection, anti-oxidation, anti-inflammatory and so on (Xiao J. Zheng, Hao Xiao, Zhi Zeng, ZiW. Sun, Can Lei, Jing Z. Dong, Ying Wang. Composition and serum antioxidation of the main flavonoids from fermented vine tea (Ampelopsis grossedentata) has also been shown. Journal of functional foods. 2014, 9, 290-294.)
Albizia julibrissin is a species of tree from the Fabaceae family, native to southwestern and eastern Asia. It is known by a wide variety of common names such as “Persian silk tree” or “pink siris”. It is widely planted as an ornamental plant in parks and gardens. The seeds of the plant are used as food for livestock and by wildlife. The extracts of Albizia julibrissin are found to have anti-depressant properties [Kim, J H; Kim, S Y; Lee, S Y; Jang, C G (2007). “Antidepressant-like effects of Albizzia julibrissin in mice: Involvement of the 5-HT1A receptor system”. Pharmacology, Biochemistry, and Behavior 87 (1): 41-7]. In traditional Chinese medicine, Albizia julibrissin is used to nourish the heart and calm the spirit. See http://www.acupuncture-and-chinese-medicine.com/albizza.html, accessed Jun. 15, 2015. It is also used for treating insomnia, injuries due to falls and removing carbuncles. “Shen Nong's Herbal Classic”, a famous Chinese ancient book, teaches its medicinal use for mental diseases. Albizia julibrissin main constituents include triterpenoid saponins, lignanoids, phenolic glycosides, flavonoids, spermine macrocyclic alkaloids and so on. Among them, the triterpenoid saponins have been proved to be the main bioactive principles of this crude drug (Kokila K, Priyadharshini S D, Sujatha V. Phytopharmacological properties of Albizia species: a review. Int J Pharm Pharm Sci 2013; 5(Suppl. 3):70-3.). Modern pharmacology studies have shown it possessed sedative, antidepressant, anti-oxidant, anti-tumor, immunomodulatory, anti-fertility and anti-platelet activating factor receptor activities. (Hongxiang Sun, Shuwang He, Minghua Shi. Adjuvant-active fraction from Albizia julibrissin saponins improves immune responses by inducing cytokine and chemokine at the site of injection. International Immunopharmacology 22 (2014) 346-355).
The skin provides a vital barrier structure that protects human from environmental insults. The epidermis, where most of the skin barrier function resides, is highly stratified and has an outermost layer that is cornified. Epidermal barrier integrity disruption or dysfunction is pathologically involved in a variety of compromised skin conditions, including dry skin, skin sensitization, atopic dermatitis, psoriasis and aging. To build a strong and improved skin barrier it is necessary to increase the threshold to defend against extrinsic stimulates. Even for compromised skin conditions, the restoration of the skin barrier is also important for recovering and reducing appearance of dry, aging, inflammation and other pathological properties.
Dry skin is a common skin condition that affects almost all of people at some times in their lives. Dry skin can cause many skin problems including atopic dermatitis, eczema, psoriasis and pruritus. The moisturizing is also a key step for an elastic and transparent skin condition, which makes skin look healthy, young and beautiful.
Inflammatory skin conditions such as atopic dermatitis, eczema and sensitive skin also have a close connection with the skin's barrier properties. Epidermal integrity is necessary for the skin to defend against external stimulants.
Filaggrin is an important protein involved in skin moisturizing and immune responses through its contribution to skin barrier structure and functions. Filaggrin can be degraded to free amino acids forming a major component of natural moisturizing factor (NMF), which serves as the primary humectant of the stratum corneum (SC). 2-pyrrolidone-5-carboxylic acid (PCA) and urocanic acid (UCA) are two important NMF components, which bind water and make the surface of normal skin soft and flexible. Filaggrin, together with NMF, contribute to stratum corneum (SC) hydration and pH. Filaggrin is different from traditional moisturizing ingredients which function to increase water absorption. Filaggrin and NMF function to improve the skin barrier function and water binding capability of the epidermis. Decreased filaggrin and NMF are mainly the key factors resulting in dry skin. Restoration or improvement of filaggrin and NMF is important for healthy and lively skin. In addition, UCA may have several other functions in SC, including UV photoprotection and as a scavenger of UV-generated hydroxyl radicals [Jacob P. Thyssen and Sanja Kezic (2014) “Causes of epidermal filaggrin reduction and their role in the pathogenesis of atopic dermatitis”. J Allergy Clin Immunol 2014; 134:792-9.].
Additionally, filaggrin is also important for the formation of the comeocyte. Filaggrin functions as an intermediate filament-associated protein (IFAP) to aggregate keratin filaments into macrofibrils, the largest filament bundles present in comeocytes. Along with several other epidermal differentiation-linked proteins, filaggrin is then cross-linked into the cornified envelope. Filaggrin contributes a strong structure that is a defense line for skin. Studies have strongly suggested that perturbation of skin barrier function as a result of reduction or complete loss of filaggrin expression leads to enhanced percutaneous transfer of allergens, further stimulation of langerhans cells which lead to Th2 immune responses. This ultimately results in the pathology of skin inflammation. Improvement of filaggrin can prevent or limit the attenuation of skin inflammation. Filaggrin is therefore in the frontline of defense, and protects the body from the entry of foreign environmental substances that can otherwise trigger aberrant immune responses [Osawa R, Akiyama M, Shimizu H (2011)“The filaggrin gene defects and the risk of developing allergic disorders.” Allergol Int. 2011 March; 60(1):1-9.].
The function and appearance of the skin may decline with age. This decline can be caused by skin barrier dysfunction. Loricrin (LOR) is another important protein that facilitates terminal differentiation of the epidermis and formation of the skin barrier. Human LOR is an insoluble protein initially expressed in the granular layer of the epidermis during cornification and comprises 80% of the total protein mass of the cornified envelope (CE). The content of LOR reduces with age [Mark Rinnerthaler, Jutta Duschl, Peter Steinbacher, Manuel Salzmann, Johannes Bischof (2013)“Age-related changes in the composition of the cornified envelope in human skin”. Experimental Dermatology, 2013, 22, 329-335]. It is therefore advantageous to promote the expression of LOR to reduce the effects of aging on the skin.
LOR, involucrin and filaggrin are cross-linked by the formation of e-(g-glutamyl)lysine isodipeptide bonds during epidermal differentiation. This function is catalyzed by transglutaminase 1 (TGM 1). Most TGM1 is anchored to the keratinocyte plasma membrane via fatty acyl linkages and can also function to crosslink lipids to the envelope. [Richard L Eckert, Michael T Sturniolo, Ann-Marie Broome, Monica Ruse and Ellen A Rorke (2005)“Transglutaminase Function in Epidermis” Journal of Investigative Dermatology (2005) 124, 481-492] Mutation or reduced amount of TGM 1 is associated with lamellar ichthyosis and other skin problems with skin barrier dysfunction. Thus an increase of TGM 1 is beneficial for improving skin strength and preventing SC from coming off.
Dry skin, aging, itching and other skin problems are related to decreased differential ability and metabolism of skin. Cell vitality is a basic source of skin physiological properties. Recovery or improvement of skin cell vitality can provide a potential differential ability and metabolism of skin, which are important for skin regeneration and defending intrinsic and extrinsic stimulate. Accordingly, it would be desirable to find active ingredients to promote filaggrin and LOR to improve skin barrier.
Applicants have surprisingly discovered that certain extracts of Ampelopsis grossedentata when combined with certain extracts of Albizia julibrissin showed unexpected synergy in providing superior skin barrier protection, reducing the signs of aging in the skin and reducing skin inflammation.